A. I. Kopeliovich

Dynamics of a spin-polarized electron liquid: Spin oscillations with a low decay

We investigate the dynamics of spin-nonequilibrium electron systems for the case when normal electron collisions prevail over the other scattering processes and the ”hydrodynamic flow” regime is realized. The hydrodynamic equations for the electron liquid have been obtained and analyzed. We demonstrate that oscillations of the spin polarization are possible in a conducting ring with inhomogeneous magnetic properties. These low-decay oscillations are accompanied by the oscillations of the drift current in the ring. We demonstrate also that the spin polarization of the electron density may be revealed via the voltage between the ends of the open circuit with an inhomogeneous spin polarization. The effect may be observed both in the hydrodynamic and diffusive regimes. 1 ar X iv :1 10 9. 18 72 v1 [ co nd -m at .m es -h al l] 9 S ep 2 01 1 Dynamics of Spin-Polarized Electron Liquid and Spin Pendulum R.N.Gurzhi, A.N.Kalinenko, A.I.Kopeliovich, P.V.Pyshkin, A.V.Yanovsky

Angle-resolved spectroscopy of electron-electron scattering in a 2D system

Electron-beam propagation experiments have been used to determine the energy and angle dependence of electron-electron (ee) scattering in a two-dimensional electron gas (2DEG) in a very direct manner. The experimental results provide direct evidence for novel ee-scattering effects in 2D degenerate conductors. Most striking is the increased importance of small-angle scattering in a 2D system with decreasing excitation energy. In particular, in a 2DEG ee-scattering can, at sufficiently low energies, be purely dephasing in character, i.e. changing the phase but not the direction of electron motion.

Dynamic spin–electric and spin–thermal effects in a system of electrons on the surface of liquid helium

A study is made of the natural spin-electric and thermoelectric oscillations in an electron ring and of forced oscillations of the spin density and temperature driven with the help of external electrodes. Effects that may be used to investigate the spin characteristics of the system, in particular, spin-flip processes, by means of electrical measurements are proposed.

Spin-Polarized Current in a Nonmagnetic Conductor and the Role of Electron–Electron Scattering

The influence of electron–electron scattering on the efficiency of certain methods for the injection and generation of spin–polarized current states in nonmagnetic conductors is discussed. We consider the effect of electron–electron collisions on the resistance to electric transport developing at the interface between a magnetic conductor (MC) and a nonmagnetic conductor (NMC). An essentially unbounded increase of the interfacial MC/NMC magnetoresistance with temperature is predicted.

On the deviations from Matthiessen’s rule in quasi-one-dimensional conductors

An explanation is proposed for the large deviation from Matthiessen’s rule observed experimentally in the quasi-one-dimensional metal NbSe3, the Fermi surface of which contains several sheets which are isolated from each other. The deviation from Matthiessen’s rule arises as a result of the nonadditive influence on the electron distribution function from processes of electron scattering on lattice defects (Se vacancies) and phonons. It is shown that the experimentally obtained temperature dependence of the electrical conductivity of NbSe3 can be described satisfactorily in the framework of a simplified model of a one-dimensional Fermi surface in the form two pairs of symmetric points in quasimomentum space. Large deviations from Matthiessen’s rule can be explained by the different character of the scattering on lattice defects and on phonons for electrons localized on different structural chains of the quasi-one-dimensional metal.

Spin field-effect transistor with electric control

The effects of spin polarization control in hybrid magnetic-nonmagnetic conductor structures have been considered. The concept of a transistor capable of generating and amplifying a spin-alternating signal has been proposed. The transistor principle is based on spatial separation of spin components and their control with electric gates in the “current-in-plane” hybrid magnetic-nonmagnetic conductor structure. This control is achieved through the effect of spin-electric signal transformation predicted in this study. Such transistor is feasible on the grounds of present-day materials and technologies.

Nanocontact spin-electric effect

It is predicted that a spin signal can be converted into a change of the electric potential. This effect arises when spin-polarized electrons from a nonmagnetic circuit N penetrate into a magnetized magnetic attachment M with Zeeman splitting of the electron spectrum. Since M possesses a high density of spin states with the same direction of the spin, the penetration of spin-polarized electrons into M results in the appearance of an electric double layer at the N–M boundary and therefore a jump in the electric potential between M and N. The predicted effect can be used for direct detection of a spin signal in nonmagnetic metals and semiconductors as well as for solving a number of problems of spintronics because of the ease with which an electric field can be controlled by currents in semiconductors.

Relaxation of high-energy quasiparticle distributions: Electron-electron scattering in a two-dimensional electron gas

A theory is developed for the evolution of the nonequilibrium distribution of quasiparticles when the scattering rate decreases due to particle collisions. We propose a ``modified one-collision approximation, which is most effective for high-energy quasiparticle distributions. This method is used to explain measurements of the nonmonotonic energy dependence of the signal of scattered electrons in a two-dimensional system. The observed effect is related to a crossover from the ballistic to the hydrodynamic regime of electron flow.

Spectroscopy of electron-electron scattering in a 2DEG

Experimentally electron-beam injection and detection via quantum point-contacts is used to investigate the scattering of a non-equilibrium electron distribution in a two-dimensional electron gas (2DEG) of a GaAs/(Ga,Al)As heterostructure. The energy dependence of electron–electron scattering processes has been studied in a weak magnetic field by investigating the detector signal. Assuming electron beams with a narrow opening angle a magnetic field B perpendicular to the 2DEG plane causes only electrons which are scattered in a point O at an angle α to reach the detector. Thus, it is possible to measure directly the energy dependence of the angular electron distribution after scattering. The experimental data give a clear evidence for the importance of small angle scattering processes in two-dimensional systems, as predicted theoretically.